The cover papers of booklets issued by authorities are subjected to a very wide variety of mechanical and thermal shocks, both during manufacture and in use. These cover papers are usually subjected to a graining operation to give them an attractive surface appearance. During the graining operation, the cover is passed between two embossing rollers where it is subjected to relatively high pressure, of about 100 bars (107 Pascals (Pa)).
In addition, such booklet cover papers are also subjected in some cases to a decoration operation in which a metallized or holographic piece of foil is applied under pressure by a hot-transfer operation. During this operation of depositing the foil, the cover passes through a press where it is subjected to relatively great pressure at relatively high temperature.
In addition, in the particular case of a passport, the booklet comprises a set of sheets or a “signature” including an end paper which is laminated to the inside face of the front flap of the cover, and a transparent film is transferred hot onto one of the inside pages or the end paper in order to protect the variable mentions that have previously been entered thereon. During the transfer operation, the passport is inserted into a laminator between two hot rolls, and the cover is again subject to non-negligible pressure. The temperature to which the cover is exposed may reach 130° C. for a period of several seconds.
Naturally, the passport must also present a lifetime of several years, in particular of ten years in Europe, and it must possess sufficient qualities of withstanding handling.
To satisfy the above-mentioned constraints, certain covers for passports are presently manufactured by impregnating a 200 micrometer (μm) thick cellulose medium with a polymer until it is saturated, and then using a scraper blade to spread a 50 μm thick covering layer on one of its faces, which covering layer is based on polymers and dyes, possibly including expanded microbeads. A varnish can then be applied to the deposited layer, in particular to make the cover glossy and to impart a degree of resistance to scratching or abrasion.
Attempts have also been made to increase the security of passports, in particular by providing them with respective radiofrequency identification devices (RFIDs) as described in U.S. Pat. No. 5,528,222. That patent describes a laminate which includes a chip and an antenna, the laminate subsequently being inserted in the front flap of the passport cover, for example. Nevertheless, that patent does not address itself in detail to the manner in which the radiofrequency identification device is finally integrated in the passport. A first drawback of such a cover with a radiofrequency identification device lies in the lack of uniformity between the thickness of the front flap and the thickness of the back flap of the passport. A second drawback comes from the fact that inserting a laminate into the passport involves an additional transformation operation on the passport assembly machine.
International patent application WO 00/26856 also mentions the possibility of providing a passport with an RFID. The chip is put into place in an opening in a polyimide or polyester film, and it is held in the opening by means of a resin.
The Malaysian passport presently in circulation is provided with a radio-frequency identification device. That identification device is inserted in the back flap of the passport during assembly, between the grained cover paper and the end paper of the set of inside pages. That radiofrequency identification device is in the form of a three-layer complex comprising a chip connected to an antenna, both being supported by a polyester film, which is itself inserted between two other polymer films for protecting the chip and the antenna. That laminate presents extra thickness over the chip. Inserting that laminate into the back flap of the passport gives rise to two types of extra thickness: there is a thickness difference of 1650 μm between the front flap and the back flap of the passport, and there is a thickness difference of 650 μm in the back flap between the zone where the chip is to be found and the zone where the antenna is to be found. The appearance of such a passport draws the attention of potential counterfeiters on the presence of the RFID device.
Finally, there exists demonstration passports in which the radiofrequency identification device is constituted merely by a tag (a polyester medium having the chip and the antenna present thereon) such as the device sold under the trademark Tag-it® by the supplier Texas Instruments, for example, which device is inserted between the grained cover paper and the end paper of the booklet that is laminated to the cover. The chip gives rise to local extra thickness of more than 200 μm and its presence can be perceived. In addition, it remains exposed to the shocks and stresses to which the passport is subjected, in particular during hot transfer of the transparent film.
International patent application WO 00/42569 discloses a label incorporating a radiofrequency identification device. That label has a layer of adhesive and a covering layer with the radiofrequency identification device chip being received therein. The chip is connected to a printed antenna. Such a label does not present extra thickness over the chip, but nevertheless it is not suitable for constituting a security device that is satisfactory for a passport since the presence of the label on one of the flaps of the passport cover would give rise to a difference of thickness between the two flaps. The appearance of such a passport would likewise draw the attention of potential counterfeiters to the presence of the RFID device.